The invention relates generally to orbital welding and more particularly to a method and apparatus for precisely cutting, fitting together, and orbitally welding thin-walled tubes, such as titanium.
Typically, welding thin-walled tubing, such as titanium, is a manual process requiring a high level of skill to accurately trim, fit, and weld the tubes. State-of-the-art autogenous orbital welding has been used to weld thicker walled pipe, but does not allow welding of thin-walled tubing due to the requirement of a tight fit-up of the mating pieces of tubing to be welded. Root gap tolerances of approximately 0.002 inch are typically required for an autogenous weld. These tolerances typically can not be achieved without hand trimming and fitting the tubing. Additionally, known collets used for welding thicker wall pipe are not suitable for welding thin-walled tubing. Known collets can not be placed on the tubing such that the tubing is held perpendicular to the axis of tungsten travel and such that the weld joint is centered under the tungsten.
Known welding of thin-walled tubing currently involves securing the tubing in a tool using bungee cords and scribing marks on the tubing using headers on the tool as a reference. Next the tubing is removed from the tool, cut on a nibbler and taken to a disk grinder where a mechanic grinds any excess tubing to the scribe line and deburs the tubing. The grinding is a very subjective process that relies on the eye-hand coordination of the mechanic. Next the part is then placed back in the tool where it is fit to an adjoining part which has undergone the same process. If the part needs further trimming, it is removed from the tool again and ground to fit, deburred again and placed back in the tool. Once the part is properly fitted, a tacking band is place on it and it is taken to a tacking table where tacking welds are placed around the weld joint through holes in the tacking band. The tacking band is then removed and the part is placed on a rack to be manually welded. Manual welding is a highly skilled process resulting in variations in the time spent welding and the quality of the weld.
Thus, it is desirable to have system and method of welding thin-walled tubing that overcomes the time and quality problems associated with known manual systems and methods. More specifically, it is desirable to have an automated system and method for orbitally welding thin-walled tubing. Therefore, the desirable system and method would accurately trim tubing such that mating parts have a gap suitable for autogenous orbital welding, accurately hold the mating tubing perpendicular to the orbital welding head, and accurately center the welding joint under the orbital welding head.
In one preferred embodiment a system is provided for cutting and orbitally welding thin-walled tubing. The system includes a plurality of clamping blocks that hold the tubing while the tubing is trimmed and orbitally welded. The system further includes at least one tooling plate to which the clamping blocks can be mounted such that the tubing is attached to the tooling plate and properly aligned for net length trimming. The system further includes a welding cassette for retaining the clamping blocks and properly aligning the tubing during orbital welding.
In another preferred embodiment a method is provided for cutting and orbitally welding thin-walled tubing using a system that includes a plurality of clamping blocks, at least one tooling plate and a welding cassette. The method involves clamping the tubing in the clamping blocks, cutting the tubing to a desired length while the tubing remains clamped in the clamping blocks, and orbitally welding mating pieces of the tubing while the tubing remains clamped in the clamping blocks.
In yet another preferred embodiment a system is provided for cutting and orbitally welding thin-walled tubing. The system includes at least one tooling plate having a plurality of bullet nose pins and connector receptors which properly align the tubing for net length trimming. Additionally the system includes a plurality of clamping blocks having a bottom half and a top half. The bottom half includes a plurality of bullet nose receivers that mate with the bullet nose pins to properly position the bottom half on the tooling plate. The bottom half is coupled to the mounting plate using a plurality of connectors interlocked with the connector receptors. The top half is coupled to the bottom half after a piece of tubing is cradled in the bottom half, thereby clamping the tubing between the bottom half and the top half and properly aligning the tubing for net length trimming. The clamping blocks are removable from the tooling plate while remaining clamped on the respective piece of tubing. Thus, the clamping blocks continue to hold the respective piece of tubing while the tubing is net length trimmed and orbitally welded.
Further, the system includes an automated cutting machine that utilizes the clamping blocks to hold the tubing in a desired position during cutting. Additionally, the cutting machine cuts the tubing such that deburring is not needed. Further yet, the system includes a welding cassette which has a first half that receives an orbital welding head and a pair of the clamping blocks which remain clamped around the respective pieces of tubing. The welding cassette further includes a second half hingedly connected to the first half such that the second half can be placed in an open position which allows the first half to receive the pair of clamping blocks, and further placed in a closed position which encloses the welding head and retains the pair of clamping blocks in a fixed position within the welding cassette. The welding cassette retains the pair of clamping blocks and respective tubing in the proper position and alignment for orbital welding.